Surgery for temporal mediobasal tumors: experience based on a series of 235 patients.

OBJECTIVE: To describe the clinical characteristics, diagnosis, various approaches, and outcomes in a retrospective review of a large series of temporomediobasal (TMB) tumors.
METHODS: Charts from 235 patients with TMB tumors were identified from the glioma and epilepsy surgery database and from the electronic operations log. Preoperative magnetic resonance imaging scans were available for all patients and postoperative follow-up was available for 155 of these patients (mean follow-up period, 59 mo; range, 2-172 mo). Preoperative symptoms, approaches, technical problems, and surgical complications are described.
RESULTS: Two hundred and thirty-five patients with intra-axial TMB tumors (mean age, 35 yr) were collected during an 11-year period. The largest tumor groups were astrocytomas (38.0%), gangliogliomas (29.8%), dysembryoplastic neuroepithelial tumor (11.1%), and glioblastomas (11.1%). The most frequent tumor location was the mesial Type A tumor (45.1%), with this type also showing the highest proportion of benign (World Health Organization Grades I and II) histological features (91.3%). Of all tumors, 76.2% were benign. Larger tumor size was associated with higher frequency of malignant histopathological findings. The leading symptom was epilepsy in 91% of patients, followed by drug-resistant epilepsy in 71.5%. Significant preoperative neurological deficits, such as hemiparesis or aphasia, were seen in 3.8% of the patients; another 12% had visual field deficits. Thirty-eight patients with low-grade tumors had undergone surgery previously. Several surgical approaches were chosen: transsylvian in 28%, anterior two-thirds temporal lobe resection in 23%, temporal pole resection in 15.3%, subtemporal in 19%, and transcortical in 6%. The most frequent neurological complications were transient: dysphasia (4.2%), hemiparesis (5%), and oculomotor disturbance (2.5%). Permanent nonvisual neurological complications occurred in fewer than 2% of the patients and significant new hemianopic defects were found in another 5.4% of the patients. The most severe complication was one intraoperative internal carotid artery lesion. One patient died.
CONCLUSION: Small tumor size, magnetic resonance imaging, and microsurgery have made resection of mostly benign TMB tumors possible in a large number of patients. This series supports the conclusion that these tumors can be operated on with a relative degree of safety for the patient, provided that the anatomy of the mesial temporal lobe and the variety of approaches are well known to the surgeon. However, because of the complex anatomic structures in the vicinity, transient neurological deterioration is not infrequent and certain neurological disturbances (e.g., quadrantanopia) even seem to be unavoidable, whereas permanent significant deficits are rare.